scholarly journals The Mean Pole of the Moon's Rotational Axis and General Selenocentric Coordinate System

1990 ◽  
Vol 141 ◽  
pp. 165-165
Author(s):  
Yu.V. Barkin
Keyword(s):  
Coordinate System ◽  
Rotation Axis ◽  
North Pole ◽  
Rotational Axis ◽  
Spherical Coordinates ◽  
The Mean ◽  
Unstable Position

One of the fundamental problems of lunar astronomy is the reduction of the coordinates of the Moon's surface, found by astronomical methods, to its mean pole. The instantaneous poles of the rotation axis and the instantaneous equator move in the Moon's body. The unstable position of this equator does not allow one to use in selenodesy the instantaneous spherical coordinates which have not been preliminarily transformed into some unified system of coordinates. Such a reduction can be made to the system of coordinates connected with the mean pole—to be definite, we shall speak about the Moon's North pole.

Mathematical Theory of Motion of Revolving Axes on the Surface of Planets

2000 ◽  
Vol 178 ◽  
pp. 619-622
Author(s):  
T.S. Kozhanov ◽  
Nizyarov N.
Keyword(s):  
Solar System ◽  
Coordinate System ◽  
Mathematical Theory ◽  
Rotation Axis ◽  
Point Of View ◽  
North Pole ◽  
The Sun ◽  
The North ◽  
Theory Of Motion ◽  
Rotational Motions

Let a planet perform translational and rotational motions in the field of solar attraction. Let’s assume that the observer on the surface of the planet, knows (even approximately) an orbit and variations of orientation. It is necessary to clarify the motion of the instanteous rotation axis on the planet’s surface from the observer’s point of view on the planet’s surface.1. The coordinate system, to describe the translational and rotational motions of planets around the Sun we shall take into account the properties of orbits of solar system planets, namely: 1)All planets move in the same direction as the Sun revolves.2)At the present time, from June until December the Earth’s inhabitants see the north pole of the Sun and during the second half of year the southern one (Beleckei 1975, Menzel 1959).

The Sun as a Magnetic Star

1976 ◽  
Vol 32 ◽  
pp. 457-463
Author(s):  
John M. Wilcox ◽  
Leif Svalgaard
Keyword(s):  
Recent Work ◽  
Rotation Axis ◽  
Polar Field ◽  
Magnetic Star ◽  
Rotational Axis ◽  
Field Variation ◽  
The Sun ◽  
Arbitrary Angle ◽  
Solar Magnetism ◽  
Oblique Rotator

SummaryThe sun as a magnetic star is described on the basis of recent work on solar magnetism. Observations at an arbitrary angle to the rotation axis would show a 22-year polar field variation and a 25-day equatorial sector variation. The sector variation would be similar to an oblique rotator with an angle of 90° between the magnetic and rotational axis.

scholarly journals Analysis and prediction of polar motion using MSSA method

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Xin Jin ◽  
Xin Liu ◽  
Jinyun Guo ◽  
Yi Shen
Keyword(s):  
Polar Motion ◽  
Rotation Axis ◽  
Moving Average ◽  
Singular Spectrum Analysis ◽  
Autoregressive Moving Average ◽  
Rotational Axis ◽  
Autoregressive Moving Average Model ◽  
System Service ◽  
Moving Average Model ◽  
Polar Motion Prediction

AbstractPolar motion is the movement of the Earth's rotational axis relative to its crust, reflecting the influence of the material exchange and mass redistribution of each layer of the Earth on the Earth's rotation axis. To better analyze the temporally varying characteristics of polar motion, multi-channel singular spectrum analysis (MSSA) was used to analyze the EOP 14 C04 series released by the International Earth Rotation and Reference System Service (IERS) from 1962 to 2020, and the amplitude of the Chandler wobbles were found to fluctuate between 20 and 200 mas and decrease significantly over the last 20 years. The amplitude of annual oscillation fluctuated between 60 and 120 mas, and the long-term trend was 3.72 mas/year, moving towards N56.79 °W. To improve prediction of polar motion, the MSSA method combining linear model and autoregressive moving average model was used to predict polar motion with ahead 1 year, repeatedly. Comparing to predictions of IERS Bulletin A, the results show that the proposed method can effectively predict polar motion, and the improvement rates of polar motion prediction for 365 days into the future were approximately 50% on average.

scholarly journals (1aR*,2R*,7S*,7aS*)-rel-3,6-Dimethoxy-2-methyl-1a,2,7,7a-tetrahydro-2,7-epoxy-1H-cyclopropa[b]naphthalene

IUCrData ◽  
2016 ◽  
Vol 1 (3) ◽  
Author(s):  
Alan J. Lough ◽  
Emily Carlson ◽  
William Tam
Keyword(s):  
Hydrogen Bonds ◽  
Dihedral Angle ◽  
Title Compound ◽  
Rotation Axis ◽  
Compound C ◽  
Benzene Rings ◽  
The Mean

In the racemic title compound, C14H16O3, the dihedral angle formed by the mean planes of the cyclopropane and benzene rings is 5.0 (2)°. In the crystal, a pair of weak C—H...O hydrogen bonds connect two molecules related by a twofold rotation axis, thus forming a dimer with anR22(10) motif.

scholarly journals The Trouble with Venus

1971 ◽  
Vol 40 ◽  
pp. 116-127
Author(s):  
Carl Sagan
Keyword(s):  
Dielectric Constant ◽  
Chemical Composition ◽  
Surface Temperature ◽  
Rotation Axis ◽  
Order Unity ◽  
Naked Eye ◽  
Atmospheric Structure ◽  
Data Points ◽  
The Mean ◽  
Temperature And Pressure

Venus is the closest planet. Its surface has never been seen at optical frequencies; nevertheless we now know with at least fair reliability, and in some cases with remarkable accuracy, its surface temperature and pressure, its atmospheric structure, its period of rotation, the obliquity of its rotation axis, the mean surface dielectric constant, its ionospheric structure, and even a little about its surface topography. And yet the clouds of Venus, visible to the naked eye and known to be clouds since the time of Lomonsov, continue to elude our efforts to understand them comprehensively. Not only do we disagree on the chemical composition of the clouds, but it is not even settled whether they are condensation clouds or non-condensable aerosols. And yet there is a very wide variety of relevant data on the clouds. Indeed, the ratio of potentially diagnostic data points to mutually exclusive hypotheses is of the order unity.

scholarly journals Inverse Fourier Transform in the Gamma Coordinate System

2011 ◽  
Vol 2011 ◽  
pp. 1-16
Author(s):  
Yuchuan Wei ◽  
Hengyong Yu ◽  
Ge Wang
Keyword(s):  
Fourier Transform ◽  
Coordinate System ◽  
Inverse Fourier Transform ◽  
Rotation Axis ◽  
General Scheme ◽  
Weight Functions ◽  
Projection Data ◽  
Parallel Beam ◽  
Beam Geometry ◽  
Parallel Beam Geometry

This paper provides auxiliary results for our general scheme of computed tomography. In 3D parallel-beam geometry, we first demonstrate that the inverse Fourier transform in different coordinate systems leads to different reconstruction formulas and explain why the Radon formula cannot directly work with truncated projection data. Also, we introduce a gamma coordinate system, analyze its properties, compute the Jacobian of the coordinate transform, and define weight functions for the inverse Fourier transform assuming a simple scanning model. Then, we generate Orlov's theorem and a weighted Radon formula from the inverse Fourier transform in the new system. Furthermore, we present the motion equation of the frequency plane and the conditions for sharp points of the instantaneous rotation axis. Our analysis on the motion of the frequency plane is related to the Frenet-Serret theorem in the differential geometry.

Human Response to Dynamic Rollover Conditions

2003 ◽  
Author(s):  
Jack Bish ◽  
Terence Honikman ◽  
Jason Sigel ◽  
Carl Nash ◽  
Donald Friedman
Keyword(s):  
Motor Vehicle ◽  
Rotation Axis ◽  
Test Subject ◽  
Rotational Axis ◽  
Human Response ◽  
Passenger Compartment ◽  
Hybrid Iii ◽  
Drop Tests ◽  
Vehicle Rollover ◽  
The Difference

To date, human responses in motor vehicle rollover accidents have been studied through the use of Hybrid III dummies in dolly vehicle rollover tests, quasi-static spit tests where the vehicle and occupant are rotated slowly about the rotation axis of the spit fixture, computer simulations and vehicle drop tests. To demonstrate human responses to dynamic rollover conditions more accurately we designed and built a fixture to accommodate a passenger compartment in a hoop structure that rotates as it translates. The rotational axis of the hoop structure is offset from the rotational axis of the passenger compartment to replicate vehicle center of gravity motion seen in dolly rollover tests. Testing showed the difference in restraint behavior depending upon whether the occupant was seated on the near (initially leading) or far side. It demonstrated that human and Hybrid III dummy neck response is very different. The human test subject received no injuries from diving into the roof of the passenger compartment even though this is the predicted injury mechanism reported in several technical papers.

scholarly journals The Period of Organization of the International Latitude Service: 1889–1899

2000 ◽  
Vol 178 ◽  
pp. 121-138
Author(s):  
E. Proverbio
Keyword(s):  
Principal Axis ◽  
Rotation Axis ◽  
Systematic Errors ◽  
Rotational Axis ◽  
The Earth ◽  
Secular Variations ◽  
Relative Motions

Around 1880, and for some time after that, the possibility of revealing a variation in latitude as a consequence of a separation of the instantaneous rotation axis from the Earth’s axis of inertia gave rise to much perplexity due to the complexity of the problem and the existence of non-negligible and hard-to-find systematic errors in observations of a personal and instrumental nature. These errors also depended on effects of refraction and imprecise knowledge of star declinations.To this must be added the fact that the very idea that the rotational axis and the axis of inertia were distinct and in relative motions raised difficult problems of a physical and theoretical nature. At that time the idea of the Earth’s rigidity was still generally accepted and, even admitting the hypothesis of an Earth endowed with sufficient elasticity and plasticity, the theory of which had been partly examined by G.H. Darwin, it was then almost impossible, just as it still is today, to create a model of the movements of mass inside the Earth which could offer an explanation of possible aperiodic and secular variations. In reality, more than on the existence of periodic variations, the attention and interest of geodesists and astronomers was in those years focused on the problem of the existence or non-existence of secular variations in the Earth’s principal axis.

Reduced conformal geometrodynamics

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040023 ◽  
Author(s):  
Andrej B. Arbuzov ◽  
Alexander E. Pavlov
Keyword(s):  
Gravitational Field ◽  
Dynamical Systems ◽  
Coordinate System ◽  
Tangent Space ◽  
Equations Of Motion ◽  
Mean Value ◽  
Hamiltonian Reduction ◽  
Square Root ◽  
The Mean ◽  
Static Background

The global time in geometrodynamics is defined in a covariant under diffeomorphisms form. An arbitrary static background metric is taken in the tangent space. The global intrinsic time is identified with the mean value of the logarithm of the square root of the ratio of the metric determinants. The procedures of the Hamiltonian reduction and deparametrization of dynamical systems are implemented. The reduced Hamiltonian equations of motion of gravitational field in semi-geodesic coordinate system are written.

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